A hard disk drive (HDD) is used for storing digital data. An HDD typically stores the data on one or more disks or platters that are made of magnetic material or have surfaces coated with a magnetizable material. Write heads are utilized by an HDD to magnetize regions of the disks to store information and read heads are utilized to detect the magnetization of a region in order to retrieve stored information.
A write current signal is used to transmit data to a write head, which then encodes the received data onto a platter. The write current signal is generated by a write driver circuit. The transmitted data is encoded by the write driver in the write current signal using current pulses, thus forming a pulse train in the write current signal. The higher the frequency of the current pulse, the faster data can be transmitted to the write head of the HDD. A constraint on increasing this frequency is the speed at which the write head is able read the data from the write current signal.
A limitation on the speed at which the write head can read incoming data from the write current signal is the imperfection of the square pulse that comprise a pulse train data transmission. Components used in commercial electronics for the generation of square waves are not capable of generating perfect square waves. In particular, the leading edge of each transition that forms a square pulse is commonly distorted. Additionally, the squares of a pulse train may be further distorted during the transmission of the data to the write head. The higher the frequency of the pulse train, the greater the distortion of the square pulses that form the pulse train.
The distortion of the pulse train is degradation of the leading edge of each transition in the pulse train is particularly problematic in HDD systems. This distortion of the leading edges delays the ability of the write head to correctly discern the new level of the write current after each transition in this signal. Rather than wait for the leading edge distortion to subside and the write current to settle, certain HDDs are configured to utilize an overshoot current. An overshoot current is added to the write current at each state transition of the write current. This serves to compensate for degradation of the leading edges of these state transition of the write current signal. The write head may then be configured to take advantage of this overshoot adjustment such that frequency of the write current signal and the speed of the write head can be increased.
Conventional HDD systems that utilize overshoot adjustments typically introduce an overshoot current at every state transition of the write current signal. Additionally, in these conventional HDD systems, an identical overshoot current is added for every overshoot adjustment to the write current signal. There is a need for HDD systems that are capable of providing a more flexible application of overshoot adjustments to the write current signal.